Vending machines for vending beverage cans and the like are generally designed such that upon payment of money the machine releases a beverage can and the like, which is conveyed to an opening so that the customer can take the can and the like from the machine.
It is clear that the vendor wants the customer to take the article for which payment was made and to prevent unscrupulous users from stealing merchandise from the machine. The vendor would also like to prevent a user from selecting and paying for the wrong merchandise.
Many vending machine mechanisms have been proposed to accomplish these goals. For example, U.S. Patent Application US2005077311 to Chang describes a coin-operated vending machine includes a one-way indexing mechanism that prevents unscrupulous users from taking out more merchandise than payment was made for. Japanese Patent Documents 2004234489 and JP2004295343 describe vending machines that only can move the vended items in one direction. A user is prevented from selecting the wrong merchandise with a one-way clutch. U.S. Pat. No. 5,531,355 describes a machine for vending stacked articles, such as newspapers, one at a time. The machine includes a mechanism that allows the vended article to issue outward, but prevents a dishonest customer from reaching through the slot to take additional papers.
However, the prior art has neglected another problem, which is in a way the opposite of the abovementioned problems, the problem being trying to prevent a person who has purchased an item from placing the item back in the vending machine. Such a problem may occur in a hotel and the like where a vending machine is in a guest room and guests can take out beverage cans and get billed at checkout time. If the possibility exists that a person can place the item back in the vending machine, a dishonest person can take out the item and yet falsely claim later that he put back the item and refuse to pay for it, so as to get around paying for the beverage can and the like at checkout.